Exothermic and Endothermic Chemical Reactions

What type of reaction is combustion, in terms of energy?

During a neutralization reaction, what happens to the temperature of the surroundings?

Which of the following is an example of an endothermic physical change?

What is the site where the reactants react in an acid-base reaction?

During an exothermic reaction, what happens to the kinetic energy of the molecules in the surroundings?

What happens to the temperature of your hands when using hand sanitizer?

What type of reaction is thermal decomposition, in terms of energy?

What is the role of water in an acid-base reaction?

What type of reaction is photosynthesis, in terms of energy?

What happens to the energy of the surroundings during an endothermic reaction?

Exothermic and Endothermic Reactions

Exothermic reactions release energy to the surroundings.
Endothermic reactions absorb energy from the surroundings.

Exothermic Reactions

Chemical changes:
- Combustion: CH4(g) + O2(g) → CO2(g) + 2H2O(g)
- Neutralization: NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
Physical changes:
- Freezing: H2O(l) → H2O(s)
- Condensation: H2O(g) → H2O(l)
- Deposition: H2O(g) → H2O(s)

Endothermic Reactions

Chemical changes:
- Photosynthesis: 6CO2(g) + 6H2O(l) → C6H12O6(s) + O2(g)
- Thermal decomposition: CaCO3(s) → CaO(s) + CO2(g)
Physical changes:
- Melting: H2O(s) → H2O(l)
- Evaporation/boiling: H2O(l) → H2O(g)
- Sublimation: H2O(s) → H2O(g)

Reaction Systems and Surroundings

In chemical reactions, the temperature measured is often that of the surroundings.
The system consists of the reactants, while the surroundings include the solvent and everything around the reaction site.

Energy Transfer

In exothermic reactions, energy is released as heat, increasing the kinetic energy of the surrounding molecules and the temperature.
In endothermic reactions, energy is absorbed from the surroundings, decreasing the kinetic energy of the surrounding molecules and the temperature.
Chemical potential energy is the energy stored in chemical bonds.
Exothermic reactions release energy, resulting in lower potential energy in the products.
Endothermic reactions absorb energy, resulting in lower potential energy in the reactants.

Identify and understand the difference between exothermic and endothermic reactions, including combustion, neutralization, freezing, condensation, and deposition.